Explosive cartridge

ABSTRACT

An explosive cartridge includes a substantially cylindrical sleeve ( 2 ) having an end wall ( 6 ) sealing a first end of the sleeve, an end unit ( 3 ) inserted in the sleeve to a certain depth in a second end of the sleeve, said end unit having an inner side ( 4 ) facing the interior of the sleeve and an outer side ( 5 ) on the opposite side of the end unit, a chamber ( 7 ) in the sleeve between said end wall and said inner side, said chamber being filled with a blasting agent ( 8 ), a channel ( 10 ) extending through the end unit between an outer mouth ( 11 ) and an inner mouth ( 12 ), said channel comprising a seat ( 13 ) for a priming cartridge ( 14 ), and a priming cartridge accommodated in the seat, said priming cartridge containing a detonating explosive for the firing of the blasting agent in said chamber. At least one spacing member ( 20 ), protruding in the axial direction, is provided on the outer side of the end wall ( 6 ) in the first end of the explosive cartridge and/or on the end unit in the second end of the explosive cartridge, such that an intermediate space ( 28 ) is formed between the outer side ( 5 ) of a first, lower explosive cartridge and the under side of the end wall of a second, upper explosive cartridge resting on the first explosive cartridge, when the two cartridges are entered in a drill hole ( 24 ) in order to be detonated, and at least one passage ( 21 ) is provided in the radial direction, passing said spacing member, allowing communication between said intermediate space and the surrounding space ( 27 ) in the drill hole.

TECHNICAL FIELD

The invention concerns an explosive cartridge including a substantially cylindrical sleeve having an end wall sealing a first end of the sleeve, an end unit inserted in the sleeve to a certain depth in a second end of the sleeve, said end unit having an inner side facing the interior of the sleeve and an outer side on the opposite side of the end unit, a chamber in the sleeve between said end wall and said inner side, said chamber being filled with a blasting agent, a channel extending through the end unit between an outer mouth and an inner mouth, said channel comprising a seat for a priming cartridge and a priming cartridge accommodated in the seat, said priming cartridge containing a detonating explosive for the firing of the blasting agent in said chamber. The conception of “blasting agent” also includes all kinds of gunpowder, or explosives as they also may be called.

BACKGROUND OF THE INVENTION

For the blasting of explosive cartridges—e.g. cartridges of the kind which are entered into drill holes for rock cracking—powder fuses or electrical fuses are conventionally employed for igniting the detonation of the blasting agent. It is also known in the art to fill up the drill hole with water or other liquid or semi-liquid fluid, and to generate a powerful chock wave of chock pulse in the fluid in the drill hole, which directly or indirectly causes the priming cartridge to detonate. SE 519 883 discloses an explosive cartridge with a priming cartridge provided for indirect detonation via a firing pin, which is triggered by a chock wave. In this case, the priming cartridge is of the rim-fire type. The drawback with this known explosive cartridge is that it is not always detonated, if several cartridges are stacked on top of one another. This is due to the fact that only the firing pin of the cartridge on top of the stack is effectively exposed to the surrounding fluid, which shall provide the necessary shock wave for causing the firing pin to initiate the detonation of the priming cartridge and thence causing the explosive cartridge on top of the stack to explode, while there is a great risk that the other explosive cartridges are not detonated.

Experiments also have been performed with explosive cartridges provided with priming cartridges of the centre-fire type, intended to detonate through direct action by the chock wave, i.e. without any firing pin but in other respects designed according to said SE 519 883. It has been proved that explosive cartridges of that type have the same drawback as those explosive cartridges which include a firing pin, i.e. the risk that not all explosive cartridges will be detonated if several cartridges are stacked on top of one another in a drill hole.

BRIEF DISCLOSURE OF THE INVENTION

It is the purpose of the invention to eliminate the above-mentioned problem. This can be achieved therein that at least one spacing member, protruding in the axial direction, is provided on the outer side of the end wall in the first end of the explosive cartridge and/or on the end unit in the second end of the explosive cartridge, such that an intermediate space is formed between the outer side of a first, lower explosive cartridge and the under side of the end wall of a second, upper explosive cartridge resting on the first explosive cartridge, when the two cartridges are entered into a drill hole in order to be detonated, and that at least one passage in the radial direction is provided, beyond said spacing member, allowing communication between said intermediate space and the surrounding space in the drill hole, such that a shock wave or shock pulse, that is generated in a liquid or gel state fluid surrounding the explosive cartridge in the drill hole, can be transmitted through said at least one passage beyond said spacing member to said intermediate space for the firing of the priming cartridge. Further features and aspects of the invention are disclosed in the dependent patent claims and/or will be apparent from the following, detailed description of a couple of conceivable embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description of a couple of conceivable embodiments, reference will be made to the accompanying drawings, in which

FIG. 1 is a side elevation of an explosive cartridge according to a first embodiment of the invention,

FIG. 2 shows an end view of the same explosive cartridge along the line II-II in FIG. 1,

FIG. 3 shows an axial section through the same explosive cartridge,

FIG. 4 shows three explosive cartridges according to the invention, stacked on top of one another in a drill hole, prepared to be fired,

FIG. 5 shows a detail of FIG. 4 at a larger scale,

FIG. 6 is a side elevation of a modified embodiment of the explosive cartridge according to FIGS. 1-3, and

FIG. 7 shows another embodiment of an explosive cartridge according to the invention, in an axial section thereof.

DETAILED DESCRIPTION OF THE INVENTION

With reference first to FIGS. 1-3, an explosive cartridge according to a first embodiment of the invention is generally designated 1. Its main parts consist of a substantially cylindrical plastic sleeve 2 having an end wall 6, sealing a first end of the sleeve, and an end unit 3 inserted in the sleeve to a certain depth thereof in the opposite, second end of the cartridge. According to the embodiment, the end unit 3 is made of a single piece of a comparatively stiff plastic material. However, an end unit 3 consisting of a plurality of components, which together form an integrated end unit, may also be conceived. The end unit 3 is pressed into the sleeve, such that it seals against the inner side of the sleeve.

The end unit 3 has an inner side 4 facing the interior of the sleeve and an outer side on the opposite side of the end unit. A chamber in the sleeve 2 between said end wall 6 and said inner side 4 of the end unit is designated 7. The chamber 7 occupies the main part of the volume of the sleeve 2 and is filled with a blasting agent 8. According to the preferred embodiment, the explosive cartridge 1 is intended to crack major pieces of rock and for this purpose gunpowder is a suitable blasting agent, e.g. nitrocellulose powder, so called NC-powder. Also e.g. dynamite, nitrolite, trinitrotoluene, and several other blasting agents may be conceived, at least for certain other applications than rock cracking.

A central channel 10 extends trough the end unit 3 between an outer mouth 11 and an inner mouth 12. A seat 13 for a priming cartridge 14 is provided in an inner portion of the channel 10. The priming cartridge 14 is arranged with moisture proof fit in the seat 13. The inner end extends a distance beyond the inner side 4 of the end unit, into the blasting agent 8 in the chamber 7. The priming cartridge 14 contains a detonating explosive for the ignition of the gunpowder 8. More specifically, the priming cartridge is of a type, which is detonated through centre firing. For the firing, no firing pin is needed. Instead, the priming cartridge 14 can be fired by a shock wave, a feature that is utilised according to the invention, as will be explained in the following. As a matter of fact, priming cartridges of the type that are used in shotgun shells may be employed. As is apparent from FIG. 3, the seat 13 has a shape which is adapted to the shape of the collar shaped, rear portion 15 of the priming cartridge. The rest of the inner portion 9 of the channel 10 has a cylindrical shape, matching the shape of the main portion of the priming cartridge 14, providing said moisture proof fit between the priming cartridge 14 and the end unit 3. Due to the fit between on one hand the cylindrical surface 16 of the end unit 3 and the inner side of the sleeve 2, and on the other hand the moisture proof seal between the priming cartridge 14 and the end unit 3 in the region of the inner portion 9 of the channel 10, a moisture proof seal is provided between the chamber 7 and the space surrounding the explosive cartridge 1, ensuring that the gunpowder will be kept dry.

The outermost portion 19 of the end unit 3 has a larger diameter than the main part of the end unit, which is inserted into the sleeve 2. A peripheral portion of said outermost portion 19 abuts on the second end of the sleeve 3 and determines the entrance depth of the end unit 3 into the sleeve.

According to the embodiment described in FIGS. 1-3, the explosive cartridge 1 is provided with three spacing members 20 protruding in the axial direction on the end unit 3 in the second end of the explosive cartridge. According to the embodiment, the spacing members 20 have the shape of substantially cylindrical bodies with a height, which approximately corresponds to the thickness of the outermost portion 19 of the end unit 3.

The three spacing members 20 are arranged peripherally and symmetrically on the outer side of the end unit 3, outside the channel 10 with reference to the radial direction, which channel contains the priming cartridge 14, such that three equally large openings, in the following also called passages, are established between the spacing members 20.

FIG. 4 shows three explosive cartridges 1 arranged on top of one another in a drill hole 24 in an object 25 that shall be cracked, e.g. a major piece of rock. The drill hole 24 has a slightly—about 10 mm—larger diameter than the explosive cartridge 1. The drill hole 24 is filled up with a liquid or possibly a gel state fluid 26, preferably water, which surrounds the explosive cartridges 1. This means that the fluid fills up the space 27 between the explosive cartridges 1 and the wall of the drill hole 24, as well as an intermediate space 28 that is established by means of the spacing members 20 between the outer side 5 of the end unit 3 of a first, lower explosive cartridge and the under side of the end wall 6 of a second, upper explosive cartridge that rests on the first explosive cartridge, when the two cartridges have been brought into the drill hole 24 in order to be detonated. The fluid 26 also fills up the outer portion 17 of the channel 10 between said intermediate space 28 and the priming cartridge 14.

The openings 21 between the spacing members 20, in other words, form passages between the gap between on one hand the explosive cartridges 1 and the drill hole wall 23 and on the other hand said intermediate space 28, allowing communication in the radial direction between the space that surrounds the explosive cartridges and said intermediate space, and hence also communication with the liquid column 29 in the outer portion 17 of the channel 10, so that a shock wave or shock pulse that is generated in the fluid 26 can be transmitted via said passages 21 and pass the spacing members 20, reaching the intermediate space 28 and thence also reach the liquid column 29 for the firing of the priming cartridge 14. In this way, all the explosive cartridges 1, which are accommodated in the drill hole 24 beneath an uppermost explosive cartridge 1, are detonated simultaneously with the uppermost, explosive cartridge. A device 31, which is shown only schematically, is provided in the upper end of the drill hole for the generation of a necessary pressure pulse in the fluid. The device 31 preferably consists of a body having a substantial mass, e.g. 20 kg, containing a starter cartridge, which is directed downwards into the drill hole 24 and can be fired at a distance by means of wire release. The device 31 is appropriately covered by a not shown blasting mat. FIG. 6 shows a modification of the explosive cartridge 1 that has been described with reference to FIGS. 1-3. The modified explosive cartridge 1′ has three spacing members 20, which are arranged symmetrically, protruding in the axial direction on the outer side of the end wall 6 in the first end of the explosive cartridge, while the second end of the explosive cartridge is void of any spacing members. In other respects, the explosive cartridge 1′ is identical with the explosive cartridge 1 according to the embodiment according to FIGS. 1-3 and it also functions in the same mode as that one. Therefore, as far as the design of the interior of the explosive cartridge 1′ is concerned, reference is made to the foregoing description of the explosive cartridge 1.

FIG. 7 illustrates the principle of the invention applied on an explosive cartridge 1″ having a priming cartridge 14″ of the rim-fire type and a firing pin 40. According to the invention, the explosive cartridge 1″ is provided with three spacing members 20 of the same design and arranged in the same mode as according to the embodiment according to FIGS. 1-3, i.e. protruding in the axial direction on the end unit 3″ of the explosive cartridge 1″. In other respects, the explosive cartridge 1″ is designed as is described in SE-C-519 883, the disclosure of which is incorporated into the present description through reference. Also with the explosive cartridge 1″, the intermediate spaces, which communicate with the surrounding fluid in the drill hole, in which the explosive cartridges are accommodated, are established between explosive cartridges that are stacked on top of one another, wherein a pressure pulse or a shock wave that is generated in the fluid is transmitted to said intermediate spaces via the passages between the spacing members 20. This provides the power which is required for breaking the safety provision of the firing pin in the weakened, fracture promoting region 41, allowing the firing pin to be propulsed forwards to fire the priming cartridge 14″. It should be mentioned in this connection that the design of the interior of the explosive cartridge 1″, which is known through said SE-C-519 883, does not form part of the present invention. Therefore, these prior art parts are not described in any detail. Also the explosive cartridge 1″ can be modified in the same way as the explosive cartridge 1′ has been modified in comparison with the explosive cartridge 1, namely by providing the spacing members 20 on the end wall in the first end of the explosive cartridge instead of locating them on the outer side of the end unit 3″ in the second end of the explosive cartridge 1″.

Also other modifications are conceivable within the spirit and scope of the invention. The number of spacing members and/or passages for the fluid between the space surrounding the explosive cartridge and said intermediate space between adjacent cartridges in a drill hole may be fewer or more than three. One may also conceive that the passages for the fluid, and thence for the shock waves, consist of openings in a continuous spacing member having the shape of a rim, which protrudes in the axial direction in the first and/or in the second end of the explosive cartridge. According to still another conceivable embodiment, the spacing members may consist of tongues, formed of end portions of the sleeve 2, protruding in the axial direction, like a crenelation. In this case, the end unit is provided with recesses for said tongues. It is also possible to provide spacing members in both ends of the explosive cartridge. It should be understood that these modifications exemplify just a few of those modifications which may be conceived within the conceptual idea of the invention. 

1-5. (canceled)
 6. Explosive cartridge comprising a substantially cylindrical sleeve having an end wall sealing a first end of the sleeve, an end unit inserted in the sleeve to a certain depth in a second end of the sleeve, said end unit having an inner side facing the interior of the sleeve and an outer side on the opposite side of the end unit, a chamber in the sleeve between said end wall and said inner side, said chamber being filled with a blasting agent, a channel extending through the end unit between an outer mouth and an inner mouth, said channel comprising a seat for a priming cartridge, and a priming cartridge accommodated in the seat, said priming cartridge containing a detonating explosive for the firing of the blasting agent in said chamber, wherein at least one spacing member, protruding in the axial direction, is provided on the outer side of the end wall in the first end of the explosive cartridge and/or on the end unit in the second end of the explosive cartridge, such that an intermediate space is formed between the outer side of a first, lower explosive cartridge and the under side of the end wall of a second, upper explosive cartridge resting on the first explosive cartridge, when the two cartridges are entered in a drill hole in order to be detonated, and that at least one passage is provided in the radial direction, passing said spacing member, allowing communication between said intermediate space and the surrounding space in the drill hole, such that a shock wave or shock pulse, that is generated in a liquid or gel state fluid surrounding the explosive cartridge in the drill hole, can be transmitted through said at least one passage beyond said spacing member to said intermediate space for the firing of the priming cartridge.
 7. Explosive cartridge according to claim 6, wherein the priming cartridge is of the centre-fire type and that it is located at a certain depth in said channel with the rear end of the priming cartridge at a certain distance from the outer side of the en unit, such that an outer portion of the channel communicates with said intermediate space and is filled up with said fluid, when said intermediate space is filled up with fluid.
 8. Explosive cartridge according to claim 6, Wherein said channel and its outer mouth are centrally situated and that said spacing members are situated outside of said channel with reference to the radial direction.
 9. Explosive cartridge according to claim 7, wherein said channel and its outer mouth are centrally situated and that said spacing members are situated outside of said channel with reference to the radial direction.
 10. Explosive cartridge according to claim 6, wherein said spacing member or members has/have a height corresponding to not more than half the length of the priming cartridge, however to at least 10% of the length of the priming cartridge.
 11. Explosive cartridge according to claim 7, wherein said spacing member or members has/have a height corresponding to not more than half the length of the priming cartridge, however to at least 10% of the length of the priming cartridge.
 12. Explosive cartridge according to claim 8, wherein said spacing member or members has/have a height corresponding to not more than half the length of the priming cartridge, however to at least 10% of the length of the priming cartridge.
 13. Explosive cartridge according to claim 6, wherein said spacing member or members has/have a length corresponding to at most the length of the outer portion of the channel between the priming cartridge and the outer side of the end unit, however to at least 10% of the length of said outer portion of the channel.
 14. Explosive cartridge according to claim 7, wherein said spacing member or members has/have a length corresponding to at most the length of the outer portion of the channel between the priming cartridge and the outer side of the end unit, however to at least 10% of the length of said outer portion of the channel.
 15. Explosive cartridge according to claim 8, wherein said spacing member or members has/have a length corresponding to at most the length of the outer portion of the channel between the priming cartridge and the outer side of the end unit, however to at least 10% of the length of said outer portion of the channel.
 16. Explosive cartridge according to claim 10, wherein said spacing member or members has/have a length corresponding to at most the length of the outer portion of the channel between the priming cartridge and the outer side of the end unit, however to at least 10% of the length of said outer portion of the channel. 